1. Field of the Invention
This invention relates to a method of depositing a metal on a surface and more particularly, to a method of selectively depositing an electroless metal deposit on a surface.
2. Discussion of the Prior Art
Heretofore, it has been known to employ a number of pretreatment or sensitization baths in effecting the electroless deposition of metals on various surfaces. Typically, such prior art sensitization baths used commercially have been expensive because they depend upon a noble metal, e.g., Pd, Pt, Ag, Au, etc., as the sensitizing component. However, recently methods have been reported in which electroless metal deposits can be applied to a broad variety of insulating substrates without the need to use expensive noble metals but on the contrary, employ reducible salt compositions of non-noble metals. U.S. Pat. Nos. 3,772,056; 3,772,078; 3,907,621; 3,925,578; and 3,930,963 disclose such methods. A problem with the methods disclosed in these patents and not recognized or addressed thereby or therein is that of humidity which affects the resultant electroless metal deposit. Also, another problem not recognized or addressed is that when a substrate has an aperture typically represented by the apertured printed wiring board substrate, a discontinuous electroless metal deposit is obtained on the walls of the aperture. Accordingly, a method of eliminating these problems is needed and is an object of this invention.